This invention relates to a device for identifying the kind of each particle based upon detection signals obtained by passing a specimen such as blood, in which plural kinds of particles such as blood corpuscles exist intermixedly, through a particle detecting device such as a flow cytometer.
With a flow cytometer, it is possible to detect each blood corpuscle in the blood and count the number of blood corpuscles and, also, to obtain various detection signals corresponding to each blood corpuscle, which signals suggest the kind corpuscle, by applying predetermined preliminary treatment to the blood. The detection signals are quantitative representations of various physical quantities (hereinunder referred to as "characteristic or physical parameters") such as scattered light intensity, fluorescence intensity, light absorption, particle diameter, particle area and N/C ratio (the ratio of nucleus and cytoplasm, when the particle is formed thereof) which suggest the kind of corresponding particle. Some methods and devices for identifying the kind of blood by corpuscle by using such detection signals have been known already as disclosed in U.S. Pat. Nos. 3,883,247 and 4,596,035, for example. According to these prior art techniques, however, sub-populations or "clusters" formed of respective kinds of blood corpuscles are sought from a frequency distribution diagram or histogram, or a correlative distribution diagram of the detection signals of a substantial number of particles in order to know quantitative proportions thereof, and it is impossible to know the kind of each blood corpuscle which is passing through a detecting area of the flow cytometer in real time fashion. It should be exceedingly advantageous for speeding up quantitative analysis of particle mixtures such as blood, if the kind of each particle passing through the detecting area of the particle detecting device such as a flow cytometer could be identified in real time fashion. However, only the following prior art system has been proposed as enabling such a speedier analysis. This system is based upon the principle that the value of each physical parameter substantially falls within a specific range relating to the kind of particle.
As shown in FIG. 1, detection signals X1 and X2 representing a suitable two of the above physical parameters are selected and their upper limits X1max and X2max and lower limits X1min and X2min, which are experientially selected for a specific kind of particle, are stored in upper limit registers 10 and 12 and lower limit registers 14 and 16, respectively. The detection signals X1 and X2 are supplied respectively to a pair of comparators 18 and 20 and another pair of comparators 22 and 24 and compared with the contents of the upper and lower limit registers 10 and 14 and the upper and lower limit registers 12 and 16. The comparators 18 and 20 deliver "high" level signals to an AND gate 26 when the signal X1 is within the prescribed range and, similarly, the comparators 22 and 24 deliver "high" level signals to an AND gate 28 when the signal X2 is within the prescribed range. The outputs of both AND gates are supplied to an AND gate 30 and, therefore, the AND gate 30 delivers a "high" level output when both detection signals are within the prescribed ranges, respectively. When the output signal of the AND gate 30 is of "high" level, it is judged that the particle which provides these detection signals shall belong to the specific kind. Although, two kinds of physical parameters are used in FIG. 1 three or more kinds of physical parameters may be used, and the accuracy of judgement will rise with the number of kinds. As is obvious from FIG. 1, however, it is judged that the particle does not belong to the specific kind in this logic circuit, if even one of the outputs of the comparators 18, 20, . . . is of "low" level. Therefore, there is a substantial chance of judging "true" as "false". However, if the prescribed range is expanded for removing the above problem, the probability of judging "false" as "true" will rise to reduce the accuracy of judgement.
As described above, the prior art technique could not obtain accurate judgement without mistake and, moreover, it could not numerically indicate the degree of certainty, or the probability of correctness, of each judgement.
Accordingly, an object of this invention is to provide an improved particle judging device which can identify the kind of each particle caught by a particle detecting device at high accuracy in real time fashion and, also, numerically indicate the probability of correctness of the judgement.